1. Field of the Invention
The present invention relates a photovoltaic device assembly, a solar cell module using the assembly and a manufacture method of the module and more particularly relates to a solar cell module in which the photovoltaic device assembly built therein is prevented from the penetrating phenomenon (a phenomenon the photovoltaic device assembly tears a coating material) and a manufacture method of the module.
2. Related Background Art
Recently, environmental issues have increasingly drawn attention and people have tended to be awaken to the matter in the world. Above all, the apprehensions about the global warming phenomenon following CO2 emission have been serious and therefore development of clean energy has highly been expected.
Further, in the situation where draining of energy resources has become a big issue, a new energy source has been required to be urgently developed. Today, as such a substituting energy source, a solar cell can be said to be an expected clean energy source owing to its safeness and easiness to be handled.
A variety of embodiments of a solar cell are available and the representative ones are as follows:
(1) a single crystal silicon solar cell;
(2) a polycrystalline silicon solar cell;
(3) an amorphous silicon solar cell (in this patent application, the definition also includes a microcrystalline solar cell);
(4) a copper indium selenide solar cell;
(5) a compound semiconductor solar cell; and the like.
Among them, a thin film crystalline silicon solar cell, a compound semiconductor solar cell, and an amorphous silicon solar cell have recently been subjected to active investigation and development in a wide sphere since they are possible to be developed at relatively low costs and to have a large surface area.
Conventionally, a constitution of a module composed of such solar cells and shown in FIG. 1 is representatively known. That is, the module is one obtained by sealing a photovoltaic device assembly 101 with a surface filler 102 and a back filler 104 in the outermost back face member 105 and coating the front face with a transparent outermost surface member 103. Further, in the case where the outermost back face member 105 has the conductivity just like a metal steel plate, an insulating material such as an electrically insulating film represented as a polyethylene terephthalate (PET) and nylon is used between the outermost back face member 105 and the photovoltaic device assembly 101.
In a solar cell module with such a constitution, generally, grass or a transparent polymer material such as a fluororesin film, an acrylic resin film and the like is used for the outermost surface member 103 and glass materials, steel sheets, hard plastics, flexible films and the like are used for the outermost back face member 105. Further, as the surface filler 102 and the back filler 104, those usable are organic resin compositions such as ethylene vinyl acetate copolymers (EVA), ethylene (meth)acrylic acid ester copolymers, ethylene (meth)acrylic acid copolymers, polyvinyl butyral (PVB) and the like.
Among them, a solar cell module using a transparent polymer material for the outermost surface member 103 and a flexible material for the outermost back face member 105 has flexibility and is light in weight and highly impact resistant as compared with that using glass for the outermost surface member.
Differing from a general solar cell equipped with a glass cover, such a solar cell module having flexibility can optionally be changed in forms. For example, if the outermost back face member 105 is made of a steel material, it is possible to curve corresponding to the flat faces and curved faces of a building and thus the solar cell module is suitable as those united with a building material. Further if the outermost back face member 105 is made of a flexible film, different from the case of using the steel material, the option of the form change is increased and the weight is light, so that the solar cell module obtained is possible to be easily attached to sheet-type outdoor leisure goods and portable goods and thus to be used in a variety of purposes.
On the other hand, the foregoing solar cell module having flexibility is inferior in durability to scratching as compared with that using glass for the outermost surface member and possible to be damaged of the element due to scratching or the like from the outside and damages of element are possible to considerably deteriorate the electric properties of the solar cell module and corrosion of metals used for the element may be promoted by permeation of water through the damaged portion. As a method for preventing such damages, there are adopted a method of adding to the surface filler 102 a reinforcing material such as the glass fiber materials and a method of increasing the hardness of the surface filler 102.
As described above, particularly in the solar cell module having flexibility, various countermeasures have so far been proposed in relation to the protection method of a photovoltaic device from the outside force.
On the other hand, it has not so much been discussed regarding a practical protection method of a solar cell module from rupture and damages attributed to the internal force of the solar cell module as compared with the protection method of a photovoltaic device from the outside face.
The rupture and damages of a solar cell module attributed to the internal force of the solar cell module are phenomena as follows.
For example, if a flexible material such as a polymer material and the like is used for the outermost surface member 103 as described before, attributed to the effects of installation, transportation, handling, and further the situation after installation of a solar cell module, a photovoltaic device assembly 101 sealed in the solar cell module penetrates the outermost surface member 103 to deteriorate the appearance of the solar cell module and further that sometimes results in material deterioration by water penetration from the torn parts in the case where the penetration takes place after installation of the solar cell module in outdoors. The same takes place also in the case where the outermost back face member 105 is a polymer material.
Such penetration is affected by a manufacture method of a solar cell module and more particularly by a lamination method for sealing the photovoltaic device assembly with the outermost surface member, the outermost back face member, and the fillers.
Generally known as a lamination method for a solar cell module are a vacuum lamination method by a double vacuum or a single vacuum chamber method, a roll lamination method using a roll laminator. In a manufacture method of a solar cell module using a flexible polymer material for either one or both of the outermost surface member 103 and the outermost back face member 105, manufacture methods using flexible materials by the roll lamination method are disclosed in Japanese Patent Application Laid-Open No. 7-193266, Japanese Patent Application Laid-Open No. 8-64852, Japanese Patent Application Laid-Open No. 9-70886, Japanese Patent Application Laid-Open No. 10-65194. As compared with a vacuum heating method, these methods make it possible to continuously supply a material, to improve the mass productivity, and to lower the manufacturing cost.
However, in the case of employing the roll lamination method, as compared with other methods, the above described penetration phenomenon of the photovoltaic device assembly tends to take place rather frequently.
The effect of the penetration of the photovoltaic device assembly affects not only the quality and the manufacture method of a solar cell module. Workers may possibly be injured and hurt if the photovoltaic device assembly is being protruded out the coating material.
Taking the above described situation into consideration, the present invention is to provide a photovoltaic device assembly from protruding attributed to the manufacture, the installation, the transportation, the handling, and the situation after the installation of a solar cell module and further to provide a photovoltaic device assembly with improved safeness at the time of handling the photovoltaic device assembly itself, to provide a solar cell module excellent in long-term reliability and to provide a manufacture method of the solar cell module.
Inventors of the present invention have repeatedly made investigations of the penetration phenomenon of a photovoltaic device assembly attributed to the internal force of a solar cell module in order to solve the above described problems and found the following.
(1) The penetration phenomenon occurs considerably depending on the shape of a photovoltaic device assembly.
(2) The penetration phenomenon is most noticeable in the peripheral parts of photovoltaic device assemblies arranges in series or in parallel in a solar cell module.
(3) In the case where a photovoltaic device assembly has a shape having a rectangular corner, the corner part is sharply projected. FIGS. 2A to 2D are diagrammatic figures showing such a state and FIG. 2A is a plan view of a solar cell module, FIG. 2B is a cross-section figure cut along the line 2B to 2B in FIG. 2A, FIG. 2C shows the solar cell module while being curved, and FIG. 2D shows the solar cell module being bent. As being shown in the figures, if the solar cell module 200 is curved or bent, the force generated at that time is converged upon the corner part 206 of the photovoltaic device assembly 201 to cause the phenomenon that the photovoltaic device assembly 201 penetrates the outermost surface member 203, the outermost back face member 205 and the fillers 202, 204. The reference numeral 207 shows the part penetrated with a photovoltaic device.
(4) Especially, in the case where a metal is used for the substrate of a photovoltaic device constituting a photovoltaic device assembly, the rupturing force which the projected part has is intense and the damage of a solar cell module by the penetration is considerably serious.
Incidentally, the shape of the peripheral parts of the photovoltaic device assembly is determined by each of the photovoltaic devices composing the photovoltaic device assembly and the shapes of these photovoltaic devices differ depending also on the embodiments of the solar cells. For example, the shape of a photovoltaic device to be used for a single crystal silicon solar cell depends on the single crystal silicon wafer shape and a CZ method (a Czochralski method) is employed as its production method. The single crystal silicon wafer is obtained by cutting a silicon ingot produced by the CZ method, and the cross-section of the wafer is circular. In the case of a circular shape, there is no possibility to cause the foregoing penetration, however the charging efficiency of the photovoltaic devices to be packed in the solar cell module tends to be deteriorated and it may results in a problems of enlargement of the solar cell module and the cost up of the module. For that, the shape of the single crystal silicon wafer is processed as shown in FIG. 3 to improve the charging efficiency and consequently, the peripheral parts of the photovoltaic device assembly in which photovoltaic devices are arranged in series or in parallel are so formed as to have rectangular corner parts to possibly cause the penetration phenomenon.
Further the reason for that the penetration phenomenon noticeably takes place in a roll lamination method which is preferable to be employed as a manufacture method of a solar cell module using a flexible polymer material for either one or both of the outermost surface member and the outermost back face member has been found owing to the following. It will be described with reference to FIG. 4. In this drawing, the reference numeral 401 denotes a photovoltaic device assembly, 402 a surface filler, 403 an outermost surface member, 404 a back filler, 405 an outermost back face member, 406 and 407 a heating and pressurizing upper roll and lower roll of a roll laminator apparatus.
It is attributed to that the roll lamination method is quite different from a vacuum heating method in a thermal compression bonding method. That is, in the case where a roll laminator is used, heat and pressure are applied partially to a layered body of a solar cell module before the thermal compression bonding. In this case, as shown in FIG. 4, local compression bonding takes place in the boundary parts of the parts where the photovoltaic device assembly 401 is sandwiched and the parts where no photovoltaic device assembly 401 exists in the layered body, so that the penetration of the outermost surface member 403 and the outermost back face member 405 is possibly caused in the peripheral parts of the photovoltaic device assembly 401. The yield ratio is also deteriorated by such penetration.
The penetration phenomenon by the photovoltaic device assembly is sometimes affected by shapes of bus bar electrodes, connection electrodes, and terminal-leading out electrodes which are disposed on the photovoltaic device assembly. That is, as shown in FIG. 5A and FIG. 5B, if rectangular corner parts exist in bus bar electrodes 503 extended to the peripheral parts of the photovoltaic device assembly 500 (500a, 500b), connection electrodes 504 for connecting the bus bar electrodes one another to connect the photovoltaic devices in series or in parallel, and terminal-leading out electrodes 505, as similar to the rectangular corner part 506 of the photovoltaic devices 501, these rectangular corner parts of these electrodes are probable to penetrate the outermost surface member or the outermost back face member depending on the thickness and the hardness of the connection electrodes and the like.
The present invention is achieved based on the above described findings of inventors of the present invention, constituted as following, and has purposes to prevent a photovoltaic device or the like from penetrating a coating material.
For such a purpose, the present invention provides a photovoltaic device assembly comprising a plurality of photovoltaic devices connected with one another, wherein no rectangular corner part is formed in the peripheral parts of the photovoltaic device assembly itself and the shape of the peripheral parts of the photovoltaic devices is composed of straight lines and curved lines connecting the straight lines to one another.
Further, the present invention provides a solar cell module comprising a photovoltaic device assembly which comprises a plurality of photovoltaic devices connected with one another and which is coated with a coating material, wherein no rectangular corner part is formed in the peripheral parts of the photovoltaic device assembly itself and the shape of the peripheral parts of the photovoltaic devices is composed of straight lines and curved lines connecting the straight lines to one another.
Further, the present invention provides a manufacture method of a solar cell module comprising a photovoltaic device assembly which comprises a plurality of photovoltaic devices connected with one another and which is coated with a coating material, wherein the photovoltaic device assembly has no rectangular corner part formed in the peripheral parts and the shape of the peripheral parts of the photovoltaic devices is composed of straight lines and curved lines connecting the straight lines to one another and the photovoltaic device assembly and the coating material are thermally compression bonded with each other by a roll lamination method.
In this case, it is preferable that no rectangular corner part is formed in the peripheral parts of the photovoltaic devices. Respectively neighboring two straight lines among the straight lines constituting the shape of the peripheral parts of the photovoltaic devices form 100xc2x0 or narrower interior angle at the crossing point of their extended lines. It is also preferable for the photovoltaic device assembly to have electrode tabs having no rectangular corner parts in the peripheral parts. The foregoing electrode tabs are each preferably any one of a bus bar electrode, a connection electrode, and a terminal-leading out electrode. The thickness of the photovoltaic devices is preferably 50 xcexcm or thicker. The substrate of each photovoltaic device is preferable to be an inorganic material. The substrate is preferable to have flexibility. The coating material is preferable to comprise a outermost surface member, a outermost back face member, and fillers. The outermost surface member is preferably of a polymer material.